Abstract
In this paper, we present a novel gain-enhanced sub-harmonic mixer based on 0.5-μm emitter width InGaAs/InP double heterojunction bipolar transistors (InP DHBTs). The proposed mixer consists of a transconductance stage and a gain-enhanced stage. A common-emitter transistor is used in the first stage to realize the sub-harmonic mixing while another common-emitter transistor is used in the second stage to remix the f LO+IF and fIF and also amplify the f 2LO+IF . For further verification, a transconductance mixer and a gain-enhanced mixer were designed and fabricated. Compared with the transconductance mixer, the gain-enhanced mixer exhibits a 6.8-dB higher conversion gain with 2-dB lower LO input power and a peak up-conversion gain of 9 dB at 213 GHz with f IF = 1 GHz, f LO = 106 GHz, and P IF = -26 dBm P LO = 3 dBm. To our best knowledge, the gain-enhanced mixing structure is proposed for the first time.
Highlights
InP double heterojunction bipolar transistors (InP DHBTs) are promising for terahertz application because of their superior electron transport properties, high breakdown voltage, and voltage handling capability [1]
IF and LO input signal at 106 GHz was generated by a signal source and a 90-110 GHz frequency multiplier module combined with a power amplifier block, FIGURE 6. (a) Measured conversion gains of two mixers versus LO input power at 106 GHz. (b) Measured conversion gains of two mixers versus LO frequency. (c) Measured output RF powers and conversion gains of the transconductance mixer with 5 dBm input LO power versus input IF power. (d) Measured output RF powers and conversion gains of the gain-enhanced mixer with 3 dBm input LO power versus input IF power. (e) Simulated output spectrum of the transconductance structure. (f) Simulated output spectrum of the gain-enhanced structure
The proposed mixer is featured by high conversion gain which owes to the high conversion efficiency of the gain-enhanced structure
Summary
InP double heterojunction bipolar transistors (InP DHBTs) are promising for terahertz application because of their superior electron transport properties, high breakdown voltage, and voltage handling capability [1]. In order to address this issue and achieve a high conversion gain, high harmonic suppression and low consumption simultaneously, a novel gain-enhanced mixing structure is proposed in this paper. A gain-enhanced mixer adopting two mixing stage was designed, abundant harmonics are generated from the first stage and converted in the second stage. Final measurement results show that the gain-enhanced mixer exhibits a 6.8-dB higher conversion gain with 2 dB lower LO input power than the transconductance sub-harmonic mixer and a 9-dB peak conversion gain at 213 GHz. The improvement of the conversion gain was mainly from the high conversion efficiency of the unwanted harmonics. Y. Li et al.: High Conversion Gain 210-GHz InP DHBT Sub-Harmonic Mixer Using Gain-Enhanced Structure.
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